Biotin (vitamin H) plays an essential nutritional role in various CO.sub.2 fixation reactions. Additionally, biotin serves an important function as a growth factor in poultry. Its relative unavailability from natural sources has spurred interest in synthetic approaches. Many syntheses of biotin are known in the literature. One common problem shared by all of these syntheses is that at some point therein the need for reduction of an unsaturated precursor, usually a thiophene precursor, arises. Because of the presence of the sulfur moiety in the thiophene ring, catalyst poisoning, where catalytic reduction means are employed, presents a formidable problem. Many solutions have been proposed. See for instance Taguchi et al. Chemistry Letters, 1974 (pages 729-730); Mozingo et al. U.S. Pat. No. 2,487,051 and Enoki et al. U.S. Pat. No. 3,905,995. However, problems such as sulfur loss, with a concomitant decrease in biotin yield, and catalyst poisoning persist.
The instant invention provides a means whereby the necessary biotin precursor hydrogenation can be accomplished without the problems realized heretofore by diacylating these precurosrs prior to hydrogenation.